I just repaired four leaky valves on my Pakcanoe. The leaks were where one poster here has said: where the valves fit over the rubber tubes that lead to the sponsons. The valves themselves didn't leak, but air was seeping out where the tubing is inserted into the valves. I talked to Mike at Pakboats, who suggested I put some glue where the tubing fits into the valve and let it flow down in there. I used two coats, and it seems to have worked.

After buying materials to make all new sponsons for the pair of Pakboat Swifts I bought last summer, I decided to make one last attempt to salvage the original, but defective, ones, before I cut them up to re-use the Boston valves on them. The recurrent problem, even after re-coating the insides with marine sealant, seemed to be that the heat-seal welded seam between the dual tube assembly kept failing due to pressure from the tubes when I pumped them up fully. As the seam ruptured between the segments. it would peel off the vinyl coating on the inside and the fabric there would slowly leak through the weave again.

So I took the deflated assembly and ran a line of stitching down the middle, directly over the welded the seam. I knew this would cause leakage due to the needle perforating the material, but I then inflated the tubes and poured 2 ounces of the marine raft sealant into each, closed the valves and tumbled and rolled them to distribute the liquid sealant evenly throughout the inside of the bladders. As expected, some of the sealant oozed out along that center stitching line. But I let the sponsons cure for two days, periodically deflating and re-inflating them so that the solvent vehicle for the sealant could evaporate.

I'm pleased to see that they seem to now be holding air pretty well for extended periods but I still hesitate to inflate them to full pressure. Before I do so I plan to paint both sides of the stitch-line with with Aquaseal to seal it up firmly. I am hoping that once this is done the sponson will be able to withstand full inflation.

I think I'm going to throw in the towel on the defective sponsons and make new ones. Stitching the central divider seam, coating the stitching with H-66 and adding a second round of internal sealant still didn't make them hold pressure. The heat-sealable nylon from DIYPackrafts in Canada is on the way.

I did use the marine raft sealant on one of the inflatable seats (same fabric as the sponsons and with the same problem of air leaks at the site of welded seams.) It seems to have worked pretty well and maintained full inflation for several days, even after I sat on it for a while. I could see where a bit of the sealant seeped through along a couple of the "quilting" seams that create the pockets in the seat.

So I still think that liquid latex sealant is a good product for pin holes and slow leaks in normal inflatables.

Even if you could make the stitched seam hold pressure, you would still have the problem that air would leak from one cell to the other. I don't see how that could be prevented. If you then puncture one cell, air would leak from both, and you would lose the security of having a backup cell.

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